Arsenic is a commonly occurring toxic metal in natural systems and the root cause of manydiseases and disorders. Vast areas of Bangladesh and West Bengal (India) are facing problem with high concentration of arsenic in their ground water that is used for drinking. The International drinking water standards set by Environmental Protection Agency (EPA) with respect to arsenic was 0.05 ppm. Recently, USEPA lowered the maximum contaminated level of arsenic in municipal drinking water from 0.05 ppm to 0.01 ppm. This review paper contains the total idea about the occurrence, toxicity behaviour and application of arsenic.